Is it possible to find a lagrangian for a system with a varible mass and have a vaild solution when you are complete? For instance, if I have a chain falling over the edge of a table or a rocket how would one approach this. Example of my thinking: For a chain falling over a table, if we assume that a sufficent portion of the entire mass is hanging over the edge (M'), than the lagrange will be something along the lines of: L=1/2 (dm/dq)*v(t)^2 + M'gl; where q is a generalized coordinate, and l is how high the object is above the ground-level. Anyone see anything wrong with this picture? Any other examples?